Sockets

A connection, between two endpoints, each with an IP address and a port

netstat is a utility that useful for viewing socket information.

• lists both unix and tcp/udp sockets
• LISTEN means a socket is accepting connections
• ESTABLISHED means connection is made and data is flowing

Unix Domain Sockets (IPC)

Inter-process communication (IPC) mechanism.

• know that they're running on the same machine, so they can omit checks otherwise done by TCP/IP sockets like NAT routing

IP Sockets (TCP/IP)

Mechanism enabling inter-process communication over the network (or same computer using the loopback interface, localhost)

• more overhead as they require multiple steps for the TCP protocol